Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS5396705 A
Publication typeGrant
Application numberUS 08/066,114
PCT numberPCT/SE1991/000847
Publication dateMar 14, 1995
Filing dateDec 9, 1991
Priority dateDec 10, 1990
Fee statusLapsed
Also published asCA2098089A1, DE69109693D1, DE69109693T2, EP0561892A1, EP0561892B1, WO1992010340A1
Publication number066114, 08066114, PCT/1991/847, PCT/SE/1991/000847, PCT/SE/1991/00847, PCT/SE/91/000847, PCT/SE/91/00847, PCT/SE1991/000847, PCT/SE1991/00847, PCT/SE1991000847, PCT/SE199100847, PCT/SE91/000847, PCT/SE91/00847, PCT/SE91000847, PCT/SE9100847, US 5396705 A, US 5396705A, US-A-5396705, US5396705 A, US5396705A
InventorsArvo Leini
Original AssigneeSandvik Ab
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Mounting base for guidebars
US 5396705 A
Abstract
A mounting base for chain saw guidebars, comprising a plate (11) with a slot (14) in which a guide piece (36) can slide in the lengthwise direction of the guidebar, said guide piece being acted on by one or more pistons (17) energized by a self-contained pressure source (19) preferably comprising a gas spring, and a valve device (18) which can be set in different positions, during sawing urging the guidebar outwards with a predetermined force and preventing displacement inwards, and during changing of saw chain or guidebar permitting displacement inwards of the guidebar while preventing the pistons (17) from urging the guidebar outwards.
Images(2)
Previous page
Next page
Claims(11)
I claim:
1. A mounting base for a chain saw guidebar, comprising:
a plate having a slot in which a guide piece on the guidebar slides in a lengthwise direction of the guidebar;
at least one piston extending from the plate into the slot for acting on said guide piece;
a valve device mounted within the plate and connected through a first fluid channel to the piston, said valve device having a plurality of positions;
a self contained pressure source mounted within the plate and connected to the valve device through a second fluid channel;
a first position of the valve device allowing fluid to move from the pressure source to the piston;
a second position of the valve device allowing fluid to move from the piston to the pressure source; and
a third position of the valve device preventing fluid from moving from the pressure source to the piston.
2. The mounting base according to claim 1, wherein the first position of the valve device allows fluid to move from the pressure source to the piston, but but not in the opposite direction; the second position of the valve device allows fluid to move in both directions; and the third position of the valve device prevents fluid from moving in any direction.
3. The mounting base according to claim 1, wherein the pressure source comprises a gas spring.
4. The mounting base according to claim 2, wherein the pressure source comprises a gas spring.
5. The mounting base according to claim 1, further comprising a manually releasable catch preventing the guide piece on the guidebar from leaving the slot.
6. The mounting base according to claim 2, further comprising a manually releasable catch preventing the guide piece on the guidebar from leaving the slot.
7. The mounting base according to claim 3, further comprising a manually releasable catch preventing the guide piece on the guidebar from leaving the slot.
8. A mounting base for a chain saw guidebar, comprising:
a plate having a slot in which a guide piece on the guidebar slides in a lengthwise direction of the guidebar;
at least one piston extending from the plate into the slot for acting on said guide piece;
a valve device mounted within the plate and connected through a first fluid channel to the piston, said valve device having a plurality of positions;
a self contained pressure source mounted within the plate and connected to the valve device through a second fluid channel;
a first position of the valve device allowing fluid to move from the pressure source to the piston, but not in the opposite direction; and
a second position of the valve device allowing fluid to move from the piston to the pressure source, but not in the opposite direction.
9. The mounting base according to claim 8, wherein the pressure source comprises a gas spring.
10. The mounting base according to claim 8, further comprising a manually releasable catch preventing the guide piece on the guidebar from leaving the slot.
11. The mounting base according to claim 9, further comprising a manually releasable catch preventing the guide piece on the guidebar from leaving the slot.
Description
BACKGROUND

Tree harvesting machines with saw chain and guidebar of types corresponding to those used with hand-held chain saws are known from among others the patents U.S. Pat. No. 3,991,799, 4,116,250, 4,161,200, 4,219,059 and 4,552,191. In these the guidebar is attached to a mounting base rotatable around the driving shaft from the motor to the drive sprocket for the saw chain. The guidebar and saw chain are advanced towards the tree to be felled by a hydraulic cylinder acting on the mounting base or a shaft connected to it.

In tree harvesting machines the saw chain is highly stressed, runs at high speeds and wears rapidly. This leads to expensive downtime for changing or tensioning of the saw chain, and to the possibility that the saw chain becomes so slack that it will jump off the guidebar.

It is important for the safety that the saw chain is tensioned with appropriate force, since too low force might allow the links of the chain to tilt and leave the guiding groove of the guidebar, and too high force will impair the lubrication of the saw chain and wear the rivets too soon.

In prior art, the tensioning force in the saw chain is normally adjusted by loosening the bolts holding the guidebar, followed by moving the guidebar lengthwise by a screw mechanism, and finally retightening said bolts. This does not ensure proper control of the tensioning force since there is no means for measuring the force, and since the force is affected by wear and temperature rise of the saw chain in use.

This adjustment procedure requires that the machine is stopped, and that the operator or another skilled person performs the adjustment with appropriate tools. The loss of production time and the need to leave the operator's cab make it likely that the adjustment is seldom done except when the saw chain or the guidebar has to be changed, which is too infrequent.

SUMMARY OF THE DISCLOSURE

The invention is a mounting base for a guidebar with an automatic tensioning device which holds the saw chain tensioned with a predetermined force without any action from the operator, and which allows a quick change of the saw chain without need for loosening of any bolts. This permits more operating time and improved lifetime of the saw chain.

Automatic tensioning of the saw chain is known in prior art from the patents U.S. Pat. No. 3,194,284 and 3,636,995, where a mechanical spring in the mounting base urges the guidebar outwards, U.S. Pat. No. 2,316,997 where a spring in the machine urges the nose part of the guidebar outwards by a lever connection, U.S. Pat. No. 2,532,981 and 4,486,963 where said nose part is urged outwards by a spring within the guidebar, and U.S. Pat. No. 3,279,508 where the whole guidebar is urged outwards by a spring in the guidebar. In practice, none of these arrangements has been a success, since a guidebar urged outwards by a mechanical spring with a force suited to the saw chain can also be urged inwards by some undesired external force acting on the nose part of the guidebar, such as when felling closely standing trees, with the result that the tension in the saw chain is lost so that it jumps off the groove in the guidebar. This can also happen if the tree to be felled leans backward and the non-cutting part of the saw chain is jammed. A method is shown in U.S. Pat. No. 4,486,963 to make the force required for inward displacement of the guidebar is higher than the force urging the guidebar outwards, but since this method depends on dry friction, it does not function properly in practice due to the effect of generous lubrication and strong vibrations in the guidebar.

The invention describes a mounting base designed to urge the guidebar outwards with a limited and predetermined force, still leaving the guidebar totally unaffected by external forces against the nose part of the guidebar.

A mounting base according to the invention comprises a rigid plate, rotatably journalled around the drive shaft. In the plate is a radial slot, along which a guide piece can slide, said guide piece being attached to the guidebar, as well as a joint where a hydraulic cylinder applies the force needed to rotate the mounting base with the guidebar. A piston extends from the plate into the slot, acting on the guide piece to urge the guidebar outwards. The pressure on the piston is hydraulically transmitted from a self-contained pressure source within the plate, said pressure source preferentially comprising a gas spring.

Between the piston and the pressure source is a valve device, adjustable with an external handle to either of three positions: closed, open or one-way from the pressure source to the piston. During sawing the valve device is in its one-way position, urging the guidebar outwards and keeping the saw chain tensioned, while external forces against the guidebar can not displace the guidebar inwards.

For changeing of saw chain or guidebar, the valve is set to its open position, and the guidebar is displaced inwards with a lever, followed by setting the valve to its closed position, thereby locking the piston in its inner position. The saw chain or the guidebar can then easily be changed.

BRIEF DESCRIPTION OF DRAWINGS

The invention is described in more detail with reference to the figures, where

FIG. 1 shows the mounting base with the drive shaft seen from below,

FIG. 2 shows the guidebar with the guide piece,

FIG. 3 the mounting base and the guidebar seen from the nose of the guidebar,

FIGS. 4 and 5 two versions of the valve device.

FIG. 6 discloses a valve having two one-way positions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows the underside of the mounting base, comprising a plate (11) rotatably journalled around a shaft (12) which at its end carries a drive sprocket (13) for the saw chain. In the plate is a radial slot (14) with fixed ribs (15). Near the periphery of the plate is a hole (16) which is part of a joint where a hydraulic cylinder applies the force needed to rotate the mounting base and the guidebar during sawing.

A piston (17) extends from the plate into the slot (14). The piston is (18) connected to a self-contained pressure source (19) in the plate (11) by means of fluid channels (41,42) and a valve device (18) said pressure source comprising a spring, which may be a mechanical spring but preferentially a gas spring with less volume and a well defined pressure. If it is not possible to fit a piston (17) of sufficient diameter within the thickness of the plate (11) two smaller pistons in parallel can be used. Adjoining the radial slot (14) is a notch (21) where a lever (20) can be temporarily attached with the help of which the guidebar (35) can be displaced inwards along the radial slot (14) for change of saw chain.

FIG. 2 shows the upper side of the guidebar (35) around the edge of which the saw chain (37) is guided in a groove, and FIG. 3 shows the plate (11) and the guidebar (35) seen from the nose of the guidebar. On the upper side of the guidebar (35) is a guide piece (36) attached, permanently by riveting or welding, or detachably by bolts.

The guide piece (36) is provided with guiding ribs (31,32) co-operating with the fixed ribs (15) of the plate (11) to make the guidebar (35) easily slideable along the radial slot (14) without change of direction. The guide piece (36) has a rear contact surface (34) where the piston (17) applies a force urging the guidebar (35) outwards until the saw chain (37) is tensioned, and a front contact surface (33) against which the lever (20) acts to displace the guidebar inwards for changing of saw chain. The ribs (15,31,32) locate the guidebar (35) far enough from the plane of the plate (11) to let the saw chain (37) run freely.

FIG. 4 shows a section through one embodiment of the valve device (18), connected to the pressure source (19) through a channel (41) and connected to the piston (17) through a second channel (42). The valve device (18) comprises two valve cones (43,44), a shaft (45) and a spring (50). The shaft (45) can be depressed to different depths by an eccentric (46) with a handle. The middle position (48) of the handle is the open position with both valve cones (43,44) free of their seats and free passage of the fluid in both directions through the valve device. In this position the guidebar (35) can be displayed inwards by the lever (20), with fluid moving from the piston (17) through the valve device to the pressure source (19). When the handle is then set to the closed position (49) the shaft (45) is further depressed by the eccentric (46) and the upper valve cone (43) closes to leave the piston (17) locked in its inner position. The saw chain is then slack and can easily be changed. In this position the guidebar (35) can also be removed for change or maintenance.

After fitting of a new saw chain or guidebar, the handle is moved to the middle open position (48) letting the piston (17) extend to tension the saw chain. During sawing the handle should be in its one-way position (47) when the lower valve cone (44) is held against its seat with a small force by the spring (50), allowing fluid to move from the pressure source (19) to the piston (17) to keep the saw chain tensioned even if the saw chain is lengthened by temperature or wear, while blocking any inwards displacement of the guidebar (35) and the piston (17).

The valve device (18) can be built with the same function from other known components, a second embodiment of which is shown in FIG. 5 comprising a rotary valve combined with a spring loaded return valve. In this embodiment the rotary valve can be set in three positions: a closed (59), an open (58) and a one-way position (57).

The valve device can also be made with two one-way positions, where in the first position fluid can move only from the pressure source (19) to the piston (17), and in the second position only from the piston (17) to the pressure source (19). This could be accomplished in a valve device according to FIG. 4 by making the upper valve cone (43) mobile to a limited extent along the shaft (45) but spring-loaded to let it be lifted from its seat by fluid moving from the piston (17) to the pressure source (19) while the handle is in the closed position (49). The open middle position (48) of the handle is then not needed. The valve device of FIG. 5 can be correspondingly modified by using two return valves, the first placed as in the figure letting the fluid move from the pressure source (19) to the channel (42) leading to the piston (17) when the handle is in the first one-way position (57), and the second placed between the rotary valve and the channel (42), letting fluid move from the piston (17) through the channel (42) and the rotary valve to the pressure source (19) when the handle is in the second one-way position (58).

FIG. 6 disclose such a valve having two one-way positions, which have been known in the art. The valve includes a pressure rod 145 that is separated from a valve body 143, 144 by a spring 151. In the first position 147, the lower valve cone 144 touches the seat but can be moved down by pressure from fluid entering through passage 141. In the second position 149, the upper valve cone 143 touches the seat but can be moved up by fluid entering through passage 142.

To prevent loss of the guidebar if the saw chain breaks, it is suitable to install a releasable catch (23) on the fixed ribs (15), keeping the guide piece (36) from sliding out from the slot (14). If the guidebar is to be changed, the catch is manually released.

The invention has been described in relation to its use in vehicle mounted tree harvester machines, but can also be used in hand-held chain saws. In such applications the plate (11) need not be rotatable, but should be attached to the motor housing, and the lever (20) for displacing the guide piece (36) can be permanently mounted. The valve device (18) and the pressure source (19) can be located in the motor housing.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2316997 *Aug 29, 1940Apr 20, 1943Reed Prentice CorpTensioning means for chain saws
US2357230 *Jun 30, 1942Aug 29, 1944William Shade RobertPower chain saw
US2532981 *Feb 9, 1946Dec 5, 1950E C Atkins And CompanyChain saw frame
US3194284 *Jun 5, 1963Jul 13, 1965Walker Charles MTension adjusting means for chain saws
US3232325 *Dec 23, 1963Feb 1, 1966Hamilton Lewis JPivot means for chain saw bars
US3279508 *Nov 26, 1965Oct 18, 1966Mcculloch CorpChain saw bar
US3636995 *Jul 2, 1970Jan 25, 1972Textron IncTensioner for saw chain
US3884266 *Apr 12, 1973May 20, 1975Kondo ShigejiDirectional-control valve
US3991799 *Apr 21, 1975Nov 16, 1976Albright Alva ZApparatus and method of felling and bunching trees
US4116250 *Oct 1, 1976Sep 26, 1978Umea Mekaniska AbTree felling unit
US4161200 *Jun 2, 1977Jul 17, 1979Albright Alva ZTree harvester and buncher
US4219059 *May 31, 1978Aug 26, 1980Albright Alva ZApparatus for harvesting and bunching trees
US4382334 *Jul 1, 1981May 10, 1983Omark Industries, Inc.Chain saw device
US4486963 *Sep 28, 1982Dec 11, 1984Meinan Machinery Works, Inc.Method and apparatus for drying veneer sheet
US4552191 *Mar 5, 1984Nov 12, 1985Olavi KuusilinnaTree harvesting device
SU745440A1 * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5533432 *May 8, 1992Jul 9, 1996Hultdin Invest AbSaw assembly
US5709254 *Jun 18, 1996Jan 20, 1998Argue; FletcherTree harvesting apparatus
US6539832 *Feb 16, 1999Apr 1, 2003Partek Forest AbHydraulic stretching device for a saw chain
US8365420 *Feb 25, 2008Feb 5, 2013Pellenc (Societe Anonyme)Tightening device with swivelling handling arm and appliance including such a device
US8495819 *Apr 6, 2010Jul 30, 2013Makita CorporationChain saw
US8672162Apr 6, 2010Mar 18, 2014Makita CorporationPower tool including a reservoir and a cap attached to the opening of the reservoir
US8931575Apr 6, 2010Jan 13, 2015Makita CorporationPower tool
US20100146801 *Feb 25, 2008Jun 17, 2010Pellenc (Societe Anonyme)Tightening device with swivelling handling arm and appliance including such a device
US20110314682 *Mar 17, 2010Dec 29, 2011Markus MaagQuick-tightening device for a chain saw and chain unit for same
US20120066917 *Apr 6, 2010Mar 22, 2012Makita CorporationChain saw
EP1057598A2 *May 22, 2000Dec 6, 2000Ponsse OYChain saw with saw chain tightening device
WO2014000949A1 *May 14, 2013Jan 3, 2014Robert Bosch GmbhPower cutting tool
Classifications
U.S. Classification30/386, 144/34.1, 83/819
International ClassificationB27B17/02
Cooperative ClassificationB27B17/02, Y10T83/7258
European ClassificationB27B17/02
Legal Events
DateCodeEventDescription
Jul 15, 1993ASAssignment
Owner name: SANDVIK AB, SWEDEN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LEINI, ARVO;REEL/FRAME:006657/0516
Effective date: 19930630
Aug 31, 1998FPAYFee payment
Year of fee payment: 4
Sep 8, 1999ASAssignment
Owner name: KAPMAN AB, SWEDEN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SANDVIK AB;REEL/FRAME:010197/0816
Effective date: 19990907
Oct 3, 2001ASAssignment
Oct 2, 2002REMIMaintenance fee reminder mailed
Mar 14, 2003LAPSLapse for failure to pay maintenance fees
May 13, 2003FPExpired due to failure to pay maintenance fee
Effective date: 20030314
Mar 8, 2005ASAssignment
May 6, 2015ASAssignment
Owner name: OMARK PROPERTIES, INC., OREGON
Free format text: RELEASE OF PATENT SECURITY INTEREST;ASSIGNOR:GENERAL ELECTRIC CAPITAL CORPORATION, AS AGENT;REEL/FRAME:035603/0495
Effective date: 20150505
Owner name: FREDERICK MANUFACTURING CORPORATION, MISSOURI
Free format text: RELEASE OF PATENT SECURITY INTEREST;ASSIGNOR:GENERAL ELECTRIC CAPITAL CORPORATION, AS AGENT;REEL/FRAME:035603/0495
Effective date: 20150505
Owner name: WOODS EQUIPMENT COMPANY, ILLINOIS
Free format text: RELEASE OF PATENT SECURITY INTEREST;ASSIGNOR:GENERAL ELECTRIC CAPITAL CORPORATION, AS AGENT;REEL/FRAME:035603/0495
Effective date: 20150505
Owner name: SPEECO, INCORPORATED, COLORADO
Free format text: RELEASE OF PATENT SECURITY INTEREST;ASSIGNOR:GENERAL ELECTRIC CAPITAL CORPORATION, AS AGENT;REEL/FRAME:035603/0495
Effective date: 20150505
Owner name: GEAR PRODUCTS, INC., OKLAHOMA
Free format text: RELEASE OF PATENT SECURITY INTEREST;ASSIGNOR:GENERAL ELECTRIC CAPITAL CORPORATION, AS AGENT;REEL/FRAME:035603/0495
Effective date: 20150505
Owner name: BLOUNT, INC., OREGON
Free format text: RELEASE OF PATENT SECURITY INTEREST;ASSIGNOR:GENERAL ELECTRIC CAPITAL CORPORATION, AS AGENT;REEL/FRAME:035603/0495
Effective date: 20150505
Owner name: FABTEK CORPORATION, OREGON
Free format text: RELEASE OF PATENT SECURITY INTEREST;ASSIGNOR:GENERAL ELECTRIC CAPITAL CORPORATION, AS AGENT;REEL/FRAME:035603/0495
Effective date: 20150505
Owner name: DIXON INDUSTRIES, INC., KANSAS
Free format text: RELEASE OF PATENT SECURITY INTEREST;ASSIGNOR:GENERAL ELECTRIC CAPITAL CORPORATION, AS AGENT;REEL/FRAME:035603/0495
Effective date: 20150505
Owner name: 4520 CORP., INC., OREGON
Free format text: RELEASE OF PATENT SECURITY INTEREST;ASSIGNOR:GENERAL ELECTRIC CAPITAL CORPORATION, AS AGENT;REEL/FRAME:035603/0495
Effective date: 20150505
Owner name: BI, L.L.C., OREGON
Free format text: RELEASE OF PATENT SECURITY INTEREST;ASSIGNOR:GENERAL ELECTRIC CAPITAL CORPORATION, AS AGENT;REEL/FRAME:035603/0495
Effective date: 20150505
Owner name: BLOUNT INTERNATIONAL, INC., OREGON
Free format text: RELEASE OF PATENT SECURITY INTEREST;ASSIGNOR:GENERAL ELECTRIC CAPITAL CORPORATION, AS AGENT;REEL/FRAME:035603/0495
Effective date: 20150505
Owner name: WINDSOR FORESTRY TOOLS LLC, ALABAMA
Free format text: RELEASE OF PATENT SECURITY INTEREST;ASSIGNOR:GENERAL ELECTRIC CAPITAL CORPORATION, AS AGENT;REEL/FRAME:035603/0495
Effective date: 20150505